Gas separation can be accomplished by passing a mixture of gases over an adsorbent material that preferentially adsorbs a more readily adsorbed component relative to a less readily adsorbed component of the mixture. Examples of such processes include temperature swing adsorption (TSA) and pressure swing adsorption (PSA). PSA generally involves coordinated pressure cycling of a gaseous mixture over an adsorbent material. The total pressure is elevated during intervals of flow in a first direction through the adsorbent bed and is reduced during intervals of flow in the reverse direction. As the cycle is repeated, the less readily adsorbed component is concentrated in the first direction, while the more readily adsorbed component is concentrated in the reverse direction.
Some examples of known PSA devices are disclosed in U.S. Pat. Nos. 7,037,358 and 7,094,275, which are incorporated herein by reference. These references, for example, disclose PSA devices capable of purifying hydrogen for use in fuel cells. This continues to be an important application of PSA technology. Other applications include, for example, the separation of carbon dioxide from methane and the purification of oxygen.
Pressure swing reactors (e.g., pressure swing reformers) also are known. Like PSA devices, pressure swing reactors generally are configured to cycle the pressure of a gaseous mixture. This pressure cycling can improve reaction yields, particularly of equilibrium-limited reactions.